1. Field of the Invention
The invention relates to a method for inspecting cigarette heads, where light radiates in at least two strip-like portions, which are incident from different directions, onto the end area of a cigarette head and light reflected from the end area is received by a detector and evaluated. Furthermore, the invention relates to an apparatus for inspecting cigarette heads having at least two light sources for illuminating a respective strip-like portion of an end area of a cigarette head from different directions, and having a detector for receiving light reflected from the end area.
2. Description of Prior Art
Inspection methods and inspection apparatuses for the contactless inspection of cigarette heads are known, in which one or more straight lines is or are radiated onto the cigarette head on the tobacco side. If the cigarette is not properly filled with tobacco, the linexe2x80x94when it is observed from a different viewing anglexe2x80x94no longer appears as a straight line but rather as a wavy line or as an interrupted wavy line. This image is acquired by a sensor. Finally, the pixels lying inside and outside a narrow region around an imaginary, theoretical straight line are counted and put into a ratio with respect to one another. If this ratio exceeds a limit value, this is suppose to indicate that a cigarette is not properly filled.
This type of inspection has the disadvantage that it is inaccurate and does not allow exact statements to be made about the state of a cigarette.
Therefore, the invention is based on the problem of improving the inspection of cigarettes and providing more accurate statements about the state of a cigarette.
In order to solve this problem, the method according to the invention is defined by the fact that, in the course of evaluation, a distance between two lines which are produced from a signal generated by the detector and correspond to the strip-shaped portions is determined in order to establish the position of that region of the cigarette head which is irradiated by the portions. Furthermore, the problem is solved by means of an apparatus according to the invention, which has an evaluation device for evaluating a signal generated by the detector, which evaluation device is designed to determine a distance between two lines which are produced from the signal and correspond to the strip-shaped portions, in order to establish the position of that region of the cigarette head which is irradiated by the portions.
The invention makes use of the insight that two light bands which run toward one another and impinge as strips of light on an object to be measured, namely a cigarette head, provide information about the distance between the object to be measured and the measuring arrangement or another fixed point, or generally about the position of the object to be measured. In this case, the distance between the two strips of light which impinge on the object to be measured provides the desired information about the position of the object to be measured.
This type of contactless inspection of cigarette heads is suitable in particular for recessed filter cigarettes or Papyrossi cigarettes, in which case, with these cigarettes, the strips of light also at least partially impinge on the end of the cigarette casing or the tip sleeve and the light reflected from these regions as well is received by the detector and evaluated. As a result, a point-like light spot is obtained when the strip of light impinges upon or intercepts the casing or tip sleeve. These point-like light spots provide an orientation point for the end of the cigarette or of the tip. The strips of light which impinge on the tobacco or filter are set back relative to the end edge of the tip in the case of these cigarettes (with a hollow tip). The depth of the tip sleeve can therefore be established from a distance between the images of these point-like light spots or strips of light on the detector.
The result of the inspection can be used to generate a error signal if a cigarette does not comply with predetermined limit values. Such an error signal leads to the ejection of a cigarette in the cigarette production or packaging process. Preferably, a formation comprising a plurality of layers of cigarettes is simultaneously inspected and, if appropriate, the entire formation is ejected if a defective cigarette occurs.